In the manufacture of belted tires and more particularly radial tires, it has been found desirable that the breaker or ply belts or the like serving as reinforcement members of tires be constructed with folded edges. This avoids sharp exposed edges. This may be done by folding the breakers or plies sharply on themselves or to wrap around the edge portions of the other contiguous breakers or plies. Hence, the formation of the desired folded edges requires turning the circumferential edge portions of the endless breaker or ply belts along a fold line so that the so turned portions overlie adjacent circumferential portions of the belts. For precision tire making, formation of sharp and precise folds is particularly important. For example, such precise and sharp folding of the belts eliminates the need for subsequent sizing and trimming of the folded belts.
Heretofore, inflatable bags or bladders have been employed in tire building and belt folding machines to fold the breaker or ply belts and to carry out various other turning operations during building of tire components. Reference may be had, for example, to applicants' assignee's U.S. Pat. No. 3,348,832, dated Apr. 15, 1969, which discloses a dual bladder construction in a tire building drum for turning a ply about a bead core to form a tire carcass. However, such machine is not designed to fold sharply a breaker or ply belt back upon itself. For examples of belt folding machines that employ inflatable bladders for folding a tire component belt back upon itself, reference may be had to the Nebout U.S. Pat. No. 3,154,455, dated Oct. 27, 1964, and Wood et al U.S. Pat. No. 3,525,655, dated Aug. 25, 1970. However, to obtain the desired folds, such machines employ rubber decks with vacuum hold downs to hold the belt to the drum and to attempt to define the fold line while the edge thereof is being folded. Unfortunately, such types of belt folding machines using rubber decks with the bladders as a continuation thereof cannot with ensured repeatability obtain a precise fold edge. Rubber is well known for its change in characteristics upon age and repeated use.
In some such prior art constructions employing inflatable bladders, the fold line may be defined solely by the configuration of the bladders. However, such construction may be undesirable because no precise unyielding fold line is provided to ensure a precise and sharp fold. Moreover, the expansion characteristics of the bladder may vary depending on ambient conditions or the condition of the bladder leading to undesirable fold dimensional variations from one cycle to the next. An exemplary belt folding machine of such prior art constructions is disclosed in Head et al U.S. Pat. No. 4,087,306, dated May 2, 1978.
Another known belt folding machine, disclosed in Irie et al U.S. Pat. No. 4,063,987, dated Dec. 20, 1977, employs complex indexed folding and wrapping devices for effecting the fold. However, such machine is somewhat complicated in construction and operation.
It is also known to provide tire building and belt folding machines which include radially expandable drum decks, and some such decks are also axially adjustable. For examples of such decks, reference may be had to the following U.S. patents: Burton U.S. Pat. No. 3,160,545, Appleby et al U.S. Pat. No. 3,784,437, Jones et al U.S. Pat. No. 3,740,293 and Gazuit U.S. Pat. No. 3,647,598.